1. Field of the Disclosure
This specification relates to a relay.
2. Background of the Disclosure
A relay is a switching element configured in such a manner that a moving core is brought into contact with a fixed core in response to magnetic force of a coil, which is generated when power is supplied to the coil, and simultaneously a shaft moves up to make a movable contactor come in contact with a fixed contactor such that current can flow.
A current flows along the relay when the fixed contactor and the movable contactor come in contact with each other. Specifically, the relay uses a permanent magnet for controlling arc which is generated upon blocking high voltage direct current (DC) power. That is, the relay uses an arc-extinguishing mechanism that the permanent magnet is appropriately disposed adjacent to the fixed contactor and the movable contactor generating the arc, and the arc is controlled, cooled and extinguished using a force decided according to strength, and direction of magnetic flux generated in the permanent magnet, a current direction, and an elongated length of the arc.
A contact surface of a moving core with a fixed core is designed into various shapes, such as a corn-like shape (FIG. 3) and a planar shape (FIG. 1), according to a product characteristic. The moving core of the planar shape illustrated in FIG. 1 is configured such that the moving core and the fixed core come in contact with each other in a flat shape. On the other hand, for the corn-like moving core illustrated in FIG. 3, for example, a triangular moving core comes in contact with a fixed core which has a shape of accommodating the moving core therein.
FIG. 1 illustrates a relay 100a having a moving core of a planar shape according to the related art. As illustrated in FIG. 1, the relay 100a includes a moving unit 140 that has a contact and is movable, a gas sealing unit that seals a space filled with arc-extinguishing gas, and a magnetic driving unit that supplies a driving force for operating the moving unit 140. Here, the moving unit 140 includes a shaft 141, a cylindrical moving core 145a that is connected to a lower portion of the shaft 141 to be linearly movable along with the shaft 141 and also movable by a magnetic attractive force from the magnetic driving unit, and a movable contactor 149 that is connected to an upper end portion of the shaft 141 to form an electric contact portion. A fixed core 143a surrounding the shaft 141 is disposed at a position facing the moving core 145a. The fixed core 143a, the moving core 145a, a second barrier 118 and the like form a moving circuit of a magnetic flux.
The gas sealing unit is located around an upper portion of the moving unit 140 so as to form an arc-extinguishing gas chamber, in which arc-extinguishing gas of the relay is hermetically stored. The gas sealing unit includes a tubular sealing member, a pair of fixed contactors 120 extending through the insulating member and airtightly coupled to the insulating member, a tubular airtight member formed in a stepped shape to airtightly seal a gap between the insulating member and the second barrier 118, and a cylinder 160 hermetically surrounding the moving core 145 and the fixed core 143 and formed of a non-magnetic material. Here, the pair of fixed contactors 120 is electrically connected with a DC power source side and a load side, respectively, via electric wires, for example.
The magnetic driving unit that opens or closes the relay by driving the moving core 145 and the movable contact 149 to be explained later using a magnetic attractive force generated therein includes an excitation coil 133 and the second barrier 118. Here, the excitation coil 133 is a driving coil provided in a lower portion of the relay. The excitation coil 133 is magnetized when a current is supplied thereto, and demagnetized when the applied current is cut off. In the relay, the magnetic driving unit generates the magnetic attractive force to supply a driving force to the moving unit for opening or closing contacts. The second barrier 118 is provided above the excitation coil 133. When the excitation coil 133 is magnetized, the second barrier 118 constructs a part of a moving path of a magnetic flux together with the moving core 145 and the fixed core 143. A lower yoke forms the moving path of the magnetic flux together with the second barrier 118, the moving core 145 and the fixed core 143 when the excitation coil 133 is magnetized.
A bobbin 131 supports the excitation coil 133 which is wound therearound. A return spring 183 supplies elastic force to the moving core 145 to return to its original position, namely, a position spaced apart from the fixed core 143 when the excitation coil 133 is demagnetized. The return spring 183 is located between the moving core 145 and the fixed core 143.
FIG. 2 illustrates the moving core 145 according to the related art, which illustrates a structure of the moving core 145 which has a step therein for the return spring 183 to be mounted thereon. However, such structure has problems, such as assembly property, durability and the like, as described hereinafter.
FIG. 3 illustrates a relay having a corn-shaped moving core 145b, which will help explaining the present invention.
Hereinafter, an operation of the related art relay having such configuration will be briefly described. When the excitation coil 133 is magnetized by receiving current, a magnetic flux generated from the excitation coil 133 moves along a moving path, which is formed by a moving core 145a, a fixed core 143a, a second barrier 118 and a lower yoke (not illustrated), so as to form a closed circuit. During this, the moving core 145a linearly moves to be brought into contact with the fixed core 143a and simultaneously a shaft 141 which is connected with the moving core 145a also moves upward along with the moving core 145a. A movable contactor 149 located on the upper end portion of the shaft 141 is then brought into contact with the fixed contactor 120. Accordingly, a DC power source side and a load side are connected, such that DC power can be supplied (i.e., On state). On the other hand, when a current supplied to the excitation coil 133 is cut off, the moving core 145a returns to its original position, at which it is spaced apart from the fixed core 143a, by the return spring 183. Responsive to this, the shaft 141 which is connected to the moving core 145a also moves downward. Accordingly, the movable contactor 149 provided on the upper end portion of the shaft 141 is separated from the fixed contactor 120 and thus the DC power source side and the load side are disconnected, such that the supply of the DC power is stopped (i.e., Off state).
When power is applied through a coil terminal, magnetic force is generated on a coil assembly, and accordingly the moving core moves upward while pushing up the shaft in a direction toward the fixed core. Here, a short-circuit performance of the relay is decided based on compressive force of two types of springs when the relay is switched on. In general, since a weight of a wipe spring 181 is considerably greater than that of the return spring 183, the short-circuit performance of the relay depends on maximum compressive force of the wipe spring. Compressive force of a spring is in proportion to maximum compressive distance, and decided based on a distance between the fixed core and the moving core and a distance between the fixed contactor and the movable contactor.
The coupling between the moving core of the planar shape and the fixed core requires for strong magnetic force between the fixed core and the moving core. The strong magnetic force allows the moving core to move the shaft, thereby short-circuiting between the fixed contactor and the movable contactor. Specifically, while the fixed core and the moving core are spaced apart from each other, the strong magnetic force is required at the beginning, which is the moment when a current is applied to a coil.
The spring is interfered by the moving core, the fixed core or the shaft, and thereby is likely to generate a deviation during its operation. Also, the spring has upper and lower surfaces both with the same flat shape, which may cause a wrong assembly when assembling the moving core.